Submerged flame burner



Nov. 14, 1950 N. SWINDIN SUBMERGED FLAME BURNER Filed June 2, 1947ATTORNEYS Patented Nov. 14, 1950 UNITED STATES PATENT OFFICE ApplicationJune 2, 1947, SerialNo. 751,807 In Great Britain June 18, 1946 7 Claims.1

This invention relatesto improvements in submerged flame burners and hasfor its objects:

(a) the elimination of "back fire through an explosive mixture ofgaseous combustion fuel under compression.

(b) to enable unfiltered and relatively dusty or tar fumed combustiongases to be employed with certainty of continuous flame production.

to obtain adequate mixing of the gas and air in the high velocity tubewithout baflies and other obstructions.

'(d) a more reliable and instantaneous method of ignition.

(6) means for rapid circulation of heated liquor around the combustionchamber.

(1) general simplification of design.

(9*) means for giving visual indication of operation.

Submerged flame burners are very largely employed in the heating anddehydration of acid pickle in iron and steel works and other corrosiveliquors, and a considerable economic advantage ensues if available gasfrom blast and other furnaces can be used.

Previous attempts to present mixed gas to burners of the above type havebeen subject to the disadvantages-of sporadic backfiring and consequentflame quench. It has been found, however, that if the velocity of thegases moving .tluough the mixing chamber exceeds the counterflow rate ofinflammation and ignition takes place at a point where the rate of flowlessens, no back firing ensues and the burner maintains a steadyinflammation when the burner is submerged. A speed of combustible gasmoving through the mixing chamber is preferably of the order of 200:feet per second. This speed may vary either up or down according to thenature of the gas used.

The invention consists in the submerged flame burner having a mixingchamber, a submerged combustion chamber and .an ignition device whereinprecompressed air and combustible gas are admixed and caused to move inthe :mixing chamber at a velocity rate greater than any counterfiow rateOf inflammation, said mixing chamber having a perforate base, said baseentering the :top of the combustion chamber and means forignition ofcombustiblegas adjacent said entry within the combustion chamber wherethe velocity-of the combustible gas is-reduced due to the '2 largediameter of the "combustion chamber relative to the mixing chamber.

The invention further comprises a periscopic indicating device in the:cover of said combustion chamber, and a perforate shroud extendingexternally surrounding said combustion chamber to promote'rapidcirculation of liquid thereabout and eliminate gas bubbles "from thebody of liquor that occur adjac'ent'the burner.

The invention further comprises means for withdrawingthe lightingelectrode from the action of "radiant heater after lighting.

In order that the invention shall be "better understood reference-ismadeto the accompanying drawings wherein:

Fig. '1 shows in sectional elevation a preferred form of the inventionand-*asapplied to any iron 'or steel pick-lingtank or other tankin whichcorrosive liquids are being treated and "concentrated.

Fig. '2 shows detail "of ignition electrode mounting in the base of "themixing chamber of the burner.

Fig. '3 shows a-crosssection 'oftheburnerhead along the line X-X ofFigure 1.

'Referring to the-'drawingand'to Fig.1 the mix-'- ing chamber tube 4 andchamber with its air and gas admission ports is mounted so as to en' terthe combustion chamber B, the latter being surrounded by a circulatingshroud C being mounted in a suitable tank D. The chamber A consists inthe form "ofa tubular entityorcasing I, that is in connection with asupply of compressed gas by conduit 2 and compressed air throughconduit3, these'con'duits 2 and 3 being connected to the tube '4 whichcommunicates'with the interior of the mixing chamber casing "I. Themixingchamber A is axially perforate a'tits upper portion and-carriesastumng b'ox 5' and a gland nut 50., through which the electrode -6passes, the said electrode 6 is insulated by a steatite sheath 8, and isshown in its operative position. The electrode 6 andits insulated sheatha pass vertically through the gland hand the stufiing box 5 and isclamped 'to a'hand lever 8a to enable said electrode to be withdrawn-upwards into the'chamber A after ignition of the gases. The base 9 ofthe chamber A is centrally perforate as at l0 through which theinsulated electrode 5 passes and terminates without the in-' sulationjust below the base '01 the chamber The walls of the said chamber A areperforated as at H, the perforations being formed immediately below theentry of the chamber A to the combustion chamber B. The diameter andnumber of the perforations I I is such that the velocity of issuing gasis high enough to throw the flame sufficiently forward to preventtransmission of heat through the metal into the chamber A.

Fig. 2 shows to a larger detail the mounting of the terminal end of thesteatite insulator 8 within the perforate base 9. The base 9 is formedwith a recess l2 coaxial with the orifice H3 and the insulator 8 isfluted at its base at l3 to allow the combustible mixture to emerge intothe combustion chamber B around the central electrode 6. The electrode 6is provided with a high tension current from an outside source and isadapted to spark across the gap to the walls [4 of the base of the bodyA at earth potential.

The chamber A is formed with a flanged plate l5 which is secured to aflanged plate l6 integral with the metallic tubular housing ll of thecombustion chamber B. The plate 16 is in turn secured to a flange I8integral with the shroud C. The flange rings l6 and it are secured tothe top flange plate IQ of the liquor tank D by means of screwed cramps36. The tank D is either lined with ebonite or equivalent acid resistingmaterial 28 or is made from stainless steel or equivalent acid resistingmateriaL' The combustion chamber B is internally provided withrefractory lining 2| which tapers slightly inwardly at the base as at 22forming an orifice slightly smaller in diameter than the body aperture23, from whichorifice the flame or hot products of combustion pass intothe body of liquid within the tank D.

The shroud C is a tubular member whose skirt 24 passes into the body ofthe liquid considerable distance below the-base of the chamber B. Theshroud C performs two functions. Firstly, it reduces vibration which, inthe absence of the shroud is soconsiderable as to give rise toconsiderable concern for the safety of the apparatus; secondly, itensures eflicient circulation of the liquid to be heated by means of thesubmerged burner, owing to the air-lift action produced. Where a deeptank is employed, it is obviously impracticable to submerge the burnerto a point near the base of the tank; equally, if the burner is onlyslightly submerged, the products of combustion, despite the rate atwhich they are produced and downwardly directed by the burner, are toobuoyant to be capable of being projected through the liquid to the baseof the tank. By the employment of a suitably long shroud, however, theproducts of combustion issuing from the burner produce a circulation ofthe liquid in the tank from the base to the top thereof. The products ofcombustion which issue from the burner nozzle at 23 are immediatelycooled to the temperature of the liquid in vessel D and by air-liftaction cause rapid circulation of the heated liquid upward in theannular space 26 and into the body of liquid in the tank D through theopenings 25. The gases are at once separated and pass away from thevessel D through suitable openings in the top thereof. The circularchamber A connects with a smaller chamber E which latter is fitted witha small diameter pipe 33 constituting a'port to the chamber B. In thecover of chamber E vertically above the metal tube 33 is a tubularfitting provided with a sight glass 30 held in position by the fitting32, and

which also supports the periscope 34. This gives Y direct visualobservation to -.the inside of the burner B. The light from theobservation glass may be passed to a photo electric cell (not shown) foreither audible warning of cessation of burning or for re-ignition of thegas. The object of making chambers A and E communicating is to keep pipe33 cool by allowing part of the mixed gases to pass through it tochamber B of the burner.

The operation of the invention is as follows:

The gas and air supplies are preferably maintained at a like pressureand at a level to give a gas movement within a mixing chamber A of 200feet per second, the speed inhibiting any backward ignition of thecombustible gas after admixture. The inflammable gases entering thecombustion chamber B through the apertures Ill and l I by reason of thedrop in velocity are there ignited by the sparking device constituted bythe central electrode 6. Inflammation proceeds in a known manner withinthe chamber B, the heat derived from combustion passing to the liquid inwhich the lower part of the burner as a whole is submerged. The heattransfer from the hot gases to the liquid is almost instantaneous andequilibrium is attained by the time the gases reach the surface. Theshroud C apart from causing circulation, is also useful for separatinggas from the liquid and prevents the discharged liquid being carriedover in the form of spray.

I claim:

1. A submerged flame burner comprising in combination, means forming acombustion chamber lined with refractory material and open at its lowerend, a mixing chamber secured in the upper end of said combustionchamber and extending into the upper portion thereof, means forintroducing a combustible gas and air mix ture into said mixing chamber,an electrical ignition device extending through said mixing chamber intosaid combustion chamber, and a tubular shroud open at its lower andupper ends and spaced from and enclosing said combustion chamber andextending beyond the lower end thereof, the lower end of said mixingchamber being formed with a plurality of openings therein of a size tomaintain the velocity of the combustible mixture issuing therefrom at arate greater than the counter-flow rate of ignition of said mixture.

2. A submerged flame burner as defined in claim 1, wherein said ignitiondevice is disposed centrally of said mixing chamber base.

3. A submerged flame burner as defined in claim 1, wherein said ignitiondevice is disposed centrally in said mixing chamber base and insulatedwith steatite.

4. A submerged flame burner as defined in claim 1, wherein said ignitiondevice comprises an electrode disposed centrally-in said mixing chamberbase and forming therewith a spark gap, and insulating materialsurrounding said electrode and formed with gas passages about its lowerterminal, said passages being adjacent to the spark gap formed by saidcentral electrode and said mixing chamber base.

5. A submerged flame burner as defined in claim 1, wherein said ignitiondevice comprises an electrode and an insulating sheath disposedcentrally in said mixing chamber base, and includ- 1; ing a gland andstufflng box through which said electrode and sheath are movable, and alever connected to said electrode and sheath whereby said electrode andsheath are removable from the action of the radiant heat of the burner.6. A submergedburner as defined in claim 1,

wherein said mixing chamber is mounted on top of said combustion chamberand communicates therewith for conducting gas and air thereto, andincluding an observation glass mounted on said mixing chamber, and apassageway connecting said mixing chamber and combustion chamberdirectly beneath said glass and through which a portion of the gas andair may pass from said mixing chamber to said combustion chamber.

7. A submerged flame burner as defined in claim 1, wherein said shroudis spaced radially from said combustion chamber to provide an annulargap therebetween, said shroud having perforations about its upperportion and having a skirt wall extending below the base of the 15Number REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 710,130 Weiss Sept. 30, 1902751,972 Berg Feb. 9, 1904 1,730,440 Smith Oct. 8, 1929 1,758,474 SeehausMay 13, 1930 1,769,833 Hammond July 1, 1930 2,375,840 Ekstrom May 15,1945 FOREIGN PATENTS Country Date 7,701 Great Britain of 1908 292,736Great Britain June 28, 1928

